OO example

Nim-for-Python-Programmers.md

@@ -86,7 +86,26 @@ You can call a proc on objects with the ```anObject.foobar()```, but you can do
 
 Nim does not have an implicit _self_.
 
-It is possible to implement object-orientation features from other languages (like C++,Java,etc. or Smalltalk,Obj-C,Ruby,etc.) through libraries, thanks to the extensive meta-programming features of Nim. These are at the moment mostly work-in-progress.
+It is possible to implement object-orientation features through libraries, thanks to the extensive meta-programming features of Nim. These are at the moment mostly work-in-progress.
+
+Object orientation example:
+
+```Nim
+type Animal = ref object of RootObj
+  age: int
+  name: string
+
+type Cat = ref object of Animal
+  playfulness: float
+
+# A proc that can access and *modify* the object
+proc increase_age(self: var Cat) =
+  self.age.inc()
+
+var c = Cat(name: "Tom")
+c.increase_age()
+echo c.name, " ", c.age
+```
 
 
 ### Inheritance